When Grateful Dead drummer Mickey Hart’s grandmother descended into the depths of dementia, she stopped speaking. Hart was caring for her at his home, but was on the verge of entering her in hospice.Then he played for her. Although she had not uttered a word for nearly a year, when he began to pound out a soft, but insistent beat, she smiled. Then, a tear came to her eye and she said clearly, over and over, “Mickey.”

“That was one of the key experiences in my life, which showed me what the power of rhythm can do,” Hart says, recalling the incident, which occurred in the early 80s. “Rhythm was reconnecting her to the world that was fading away.”

Our lives, it turns out, depend deeply on rhythm. There’s the obvious lub-dub of the heart, where one lapse in essential time-keeping can be fatal; then there is the clear patterning of women’s monthly cycles. But less visible are the daily and nightly peaks and valleys of hormone levels, the critical rhythms that shape language and nonverbal communication and the ebb and flow of constantly thrumming and pulsing nerve activity in the brain.

“Brain activity fluctuates— it oscillates in rhythmic patterns and different rhythms are represented throughout the brain in terms of how its activity changes over time,” says Adam Gazzaley, director of the Neuroscience Imaging Center at the University of California San Francisco.

Gazzaley and Hart have collaborated to try to understand the neuroscience of rhythm and to plumb these patterns for potentially therapeutic uses. This fall, they spoke together at the annual conference of the AARP, using the latest imaging technology to broadcast images of Hart’s brain rhythms live.

“It was very profound,” Hart says of seeing his brain rhythms displayed as he stood on stage, “It was me. That’s what really makes me, me. It’s also what makes us, us. It’s rhythm central, it is life itself.”

For Hart, however, the experience with his grandmother left a deeper impression unlike anything he had witnessed before, despite his thousands of intense encounters with the power of music to unify and heal. “When you have your grandmother sitting in front of you and you play a drum to her and no one else is around and it makes a reaction, kind of like a reverberation, this rhythm has allowed you to talk. Now, that’s something to be noted. I want to know why and how that happened.”

Hart’s experience with his grandmother isn’t unique: physicians and music therapists have long known that rhythmic music can reach into some primal place and sometimes temporarily restore functions thought to be lost in people with dementia, Parkinson’s disease, brain injury and other devastating disorders, as well as help ease anxiety and depression associated with life-threatening illnesses like cancer.

Rhythm’s role, it seems, starts at the very earliest stages of life. In the womb, for example, the fetal heartbeat often synchronizes with the maternal heart rate. “It’s wonderful and fascinating,” Gazzaley says.

Rhythms that mimic the maternal heartbeat are often very soothing to babies after they are born, but it’s not known exactly how heart rate synchrony— or lack of it— affects the developing brain. “Most people agree that for the brain to become rhythmically appropriate in how it responds to the environment may prove to be an important part of development,” Gazzaley says.

Later in life, this lack of synchrony may contribute to certain disorders of the brain that music, with its regular rhythms, may address. “I saw one very eminent man who had become quite demented become incredibly animated,” says neurologist and author Oliver Sacks, describing a response to Hart’s drumming that he witnessed. “[The man] was also quite lucid and funny and himself for some minutes afterwards. It was extraordinary to have this sort of lasting effect.”

Neither Sacks nor other neuroscientists can explain why or how this works— or how to best harness this potentially restorative power to reduce ongoing neural decline in a sustainable way.

Some experts believe that external rhythm temporarily helps to recalibrate some of the dysfunctional internal pacemakers that regulate nerve networks that govern major brain functions like language and movement. “Rhythm enforces participation. You have to synchronize with the rhythm,” says Sacks.

“Different rhythms in the brain are associated with different cognitive operations like perception, attention and memory,” Gazzaley says, “More data is accumulating to show that [these rhythms] are causally related to how we think.”

That view has precedent in neuroscience; changing brain rhythms have long been known to be associated with varied states of consciousness, for example: the EEG, or electroencephalogram, measures these patterns of electrical activity by placing electrodes on the head and scalp. Although people tend to think of EEG in relation to sleep and dream states, it can also offer insight on what the awake and alert brain is doing. Alpha rhythms are generally linked with tuning out the external world and focusing within, while theta rhythms generated from the middle of the brain’s frontal area are associated with paying attention and deliberate planning.

And when one brain region signals another, the message comes through with greater clarity if the two are in sync rhythmically. “If their rhythms are locked in time, then they seem to communicate with each other more efficiently, so it’s part of how the brain works in a fundamental way,” Gazzaley says.

Conditions such as dementia and Parkinson’s may involve some level of asynchrony with certain regions of the brain, contributing to the disordered thinking and movement that are characteristic of these conditions. “With Alzheimer’s or Parkinson’s or [even] ADHD, there are different rhythmic patterns,” says Gazzaley. Or, as Hart puts it, “When it’s in rhythm, it’s functional. When it’s an arrhythmia or some chaos or something, then you fall into disease, you fall into ill health. Good rhythm, good health. Bad rhythm, bad health. I mean that’s the dumbed down version of what we’re after.”

Gazzaley and Hart are studying whether providing the right external source of rhythm might help a wounded brain enter a state of consciousness that it can no longer sustain on its own. The study of rhythm and music therapy, however, is still in its infancy. One challenge in conducting rigorous trials with reliable results centers around the fact that music stirs emotion, for example, and emotion alone can improve memory.

But neither Gazzaley nor Hart are deterred. While not all trials are properly controlled to asses the effect of just music alone, studies do hint that music therapy may improve gait following stroke and increase quality of life while cutting cancer pain and anxiety.

Gazzaley and Hart want to understand how it does so, with the ultimate goal of one day helping doctors to “prescribe” particular rhythms or patterns to alleviate particular conditions. “It’s not the art of music so much that we’re after but it’s the science of music,” Hart says, “That’s what will explain what we professionals already know but we don’t know how to repeat. What is the code? What’s the musical DNA? What’s the rhythm genome? That’s what Adam Gazzaley and I will hope to find.”

He adds, “We know that music makes us feel good. We know it makes us dance. We know it makes us happy and gives us pleasure. But what do we know about the healing qualities of it? Well, that’s the great frontier for music in this century.”